RR185 - Field Studies of the Effectiveness of Concrete Repairs

Phase 3a Report: An investigation of the performance of repairs and cathodic protection (CP) systems at the Dartford West Tunnel

Presents the findings of Phase 3a of the project Field Studies
of the Effectiveness of Concrete Repairs. Phase 3a involved
recovery of core samples, rectangular sections of the deck and
pieces of the cathodic repair systems. The samples were analysed
using several specialist techniques:

petrography revealed that the sprayed concrete repairs had
effectively prevented ongoing corrosion of the embedded
reinforcement,

electron microscopy found abundant evidence of redistribution
of ions within the paste in areas with CP,

pull-out resistance testing found no evidence that CP had
affected the bond strength for plain round bars in the original
deck concrete or the sprayed concrete.